This application claims the benefit of Korean Patent Application No. 10-2005-0108074, filed on Nov. 11, 2005, respectively, in the Korean Intellectual Property Office, the disclosure of which are incorporated herein in their entirety by reference.
1. Field of the Invention
The present invention relates to an M-ary phase shift keying (M-PSK) system, and more particularly, to an apparatus and method for estimating a quadrature error caused by demodulating a M-PSK signal and improving a symbol error rate caused by the quadrature error.
2. Description of the Related Art
M-ary phase shift keying (M-PSK) systems are classified into quadrature phase shift keying (QPSK) systems, 8-PSK systems, 16-PSK systems, etc. according to modulation level values M. Most wireless communication systems use QPSK, whereas a recently published enhanced data for global evolution (EDGE) standard adopts 8-PSK to increase transmission speed.
Research into the performance of modulation methods of higher M values in high speed wireless communication has been conducted. M-PSK systems have quadrature errors due to the imperfect performance of 90-degree phase shifters. A quadrature error indicates a phase shift between I channel signals and Q channel signals of receivers over 90 degrees. As the quadrature error increases, the symbol error rate performance of the M-PSK systems deteriorates.